January 1, 2010
RECORD COLD DECEMBER
By, Steve Pierce
* December 2009's monthly mean temperature at the Portland International Airport (PDX) was 35.6 degrees, nearly 5 degrees below normal. This is the 4th coldest December in history at PDX, trailing only 1990, 1985 and 1978.
* PDX recorded the single highest number of sub-freezing (32 or colder) December overnight low temperatures in nearly 25 years. There were 19 days with overnight lows at or below 32 degrees at PDX in December of 2009. The last time PDX saw more sub-freezing overnight lows in the month of December was in December 1985 when PDX recorded 25 days at or below 32 degrees.
* December 2009's mean temperature at PDX is in stark contrast to what is typical of an El Nino. Neither 1978, 1985 nor 1990 were El Nino's.
Note - The period of record used for this analysis is 1940-2009.